This invention generally relates to valves and more particularly to a valve construction which will automatically either open or close in response to a predetermined ambient temperature level. Thermally responsive values of this type are in common use and include, for examples, those which assure the shutdown of lines carrying flammable or toxic materials in the event of a fire and those which will activate a sprinkler system.
Valves of this type generally include a housing having a flow path defined therethrough in which a valve member such as a stem or stem portion is aligned to move between first and second operational positions to either initiate or shut off fluid flow dependent on the particular type action desired. Thus, for a sprinkler system the first or normal position of the valve member would be in a closed attitude and movable to a second or operational position wherein the valve member permits fluid flow therethrough. The opposite action would, of course, take place with shut off type valves.
A spring or other resilient means is utilized to urge the valve to its second position, but the thrust of such resilient means is normally counteracted by restraining means engaged with the member so as to normally block is movement to the second position, i.e. the open position in a sprinkler type system. In order that the valve assembly may move to its second or open position, such restraining means includes a fusible link, the arrangement being such, that so long as the link is intact, the valve mechanism is maintained in its first position. Upon fusing or melting of the link due to the presence of a predetermined ambient temperature level, the restraining means is released and the movement of the valve member to the second or operational position is automatically achieved by reason of the urging action of the spring.
An example of one such device is that shown in U.S. Pat. No. 3,916,930 issued Nov. 4, 1975. Therein, a lever arm which forms a portion of the fusible link is in direct contact with the valve member to restrain its movement to the second position. In this and other similar constructions, it is necessary to couple or match the capability of the fusible link to withstand the mechanical force tending to separate such with the strength of the force applied thereto by the urging means, i.e. the spring force. Accordingly, various size and strength link assemblies are produced, each fusible at a particular temperature level for application with different size and strength valves. Thus, in order to restrain the relatively high urging force, as found in a relatively large valve, it would be necessary to couple with such devices, a relatively large and accordingly more expensive link assembly. In accordingly would be more desirable if relatively lightweight and, accordingly, less expensive link assemblies could be utilized for a wider range of valve applications, particularly those having relatively strong urging springs. It is accordingly a primary object of the present invention to produce a thermally responsive valve mechanism in which the restraining means normally acting to prevent movement of the valve member to the second or operational position includes in part, frictional forces which must be overcome and thus through the mechanical advantage created thereby, enables a relatively lightweight fusible link assembly to maintain the valve member in the first or normal position thereof against the urging of a relatively strong force.
Another object of the present invention is the provision of a thermally responsive valve mechanism in which the force applied by restraining means normally preventing movement of a valve member from a first to a second position is adjustable in such a manner that a single fusible link assembly may be utilized with valve assemblies having different strength urging means.
A still further object of the present invention is the provision of a thermally responsive valve mechanism having high reliability and trouble-free performance, which is not overly complex in construction and which enables utilization of presently available components.
These and other objects of the present invention are accomplished by the novel restraining means engaged with the movable member of a valve assembly so as to normally block movement to a second position and including thermally releasable tension means having an intermediate fusible link supporting said restraining means in a first or normal position, which restraining means further includes movable means in frictional engagement with retaining means an movable thereacross such that a mechanical advantage created thereby permits a relatively mechanically weak link to withstand the force applied thereto by a relatively strong valve member urging force whereby when such link fuses due to the presence of a predetermined level of ambient temperature, the tension exerted on such link causes it to separate and, thus, release the restraining means and in turn permit the valve member to move by action of the urging means to the second position.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawing.